EP0690780B1 - Three-dimensional object production process - Google Patents

Abstract

A process for producing a three-dimensional object by successively solidifying individual layers of the object made of a liquid or powdery material by electromagnetic radiation has the disadvantage that the object either is deformed because of material shrinkage or has a lower quality surface when it is designed so as to reduce material shrinkage. To solve this problem, each layer is subdivided into an inner core zone (2) and into an outer enveloping zone (3). Exposure to radiation is differently controlled in the core zone and in the enveloping zone in order to generate different properties in each zone.

Description

The present invention relates to a method for manufacturing a three-dimensional object according to the generic term of Claim 1.

Such a method is known from EP 0 171 069 A. With such a method, a good surface can be used can be obtained, but the problem arises that a Dimensional accuracy of the object due to the deformation of the individual Layers not guaranteed due to material shrinkage is. The manufacturing time is also long.

From EP 0 362 982 A it is known to reduce the Deformation either initially to individual strips solidify that with neighboring and underlying Stripes are connected only via a support structure, or to solidify the layer only in areas, whereby in the object Columns arise between the areas. In both cases however, high surface quality cannot be obtained.

EP-A-0 429 196 describes a method according to the preamble of Claim 1 known. Avoiding the occurrence of delay and deformation in the formed object is however in the in described in this document achieved by a layer is exposed in such a way that a boundary vector is exposed and the interior by means of different Techniques is partially exposed.

WO 92/20505 also describes a method for manufacturing of a three-dimensional object.

WO 92/08200 also describes a method according to the preamble of claim 1 known. Stages by successive Layers are created on the surface through special techniques of additional exposure of the step area balanced.

It is an object of the invention, a method of the above Art to improve such that a small deformation of the Object with high surface quality at the same time becomes. Furthermore, the accuracy of the surface should be increased and material consumption and construction time are reduced.

This object is achieved by a method with solved the features of claim 1. Further training is in the dependent claims.

The invention is further illustrated by an embodiment explained with reference to the figure, which is in schematic Representation of a section through part of the object shows in a layer plane.

The inventive method works according to the The term "stereography" or "stereolithography" is known Processes as described, for example, in EP-A-0 171 069 is. This is done on a carrier or one already solidified layer a layer of a liquid or powdered material applied and by irradiation with a directed light beam, for example a laser places corresponding to the object. By doing so Solidify a multitude of layers of the object created in layers. For a more detailed description of this The method is referred to the aforementioned EP-A-0 171 069, which should be part of this application.

A partial view of an example of a selected layer is shown in the figure on the basis of which the invention The procedure should first be described in principle. In the Figure denotes line 1 the contour of the to be manufactured Object in the layer. The area of the layer is grid-like in a variety of square or rectangular Individual areas or voxels i, j .... i + 6, j + 6 with one Side length from 0.1 to 5mm, preferably 0.5 to 2mm, divided. The coordinate data of contour 1 and the individual Individual areas are available in a computer that receives the radiation the shift controls. A comparison is made in the computer the contour data with the coordinate data of the individual areas. If the computer determines that a single area, for example the individual area i + 1, j, completely within the contour 1, then this individual area becomes a core area 2 assigned; however, it is found that a single area, for example the individual area i, j, of the contour 1 is cut, then this single area becomes an envelope area 3 assigned. This results in a narrower Envelope area 3, which along the contour line 1 with a on average approximately corresponding to the side length of the individual areas Width extends.

The calculation is preferably carried out exclusively in the computer the core area 2; the envelope area 3 is then through Subtraction of the individual areas of core area 2 from the whole body calculated. When calculating the core area 2 all individual areas are marked which are fully inside the Body section, i.e. the contour line 1.

The individual areas are assigned to Shell or core, however, not just two-dimensional, like Explained in principle above, but three-dimensionally, in order to defined thickness of the envelope area 3 in all three spatial directions to obtain.

In this case, contour line 1 corresponds to a contour surface and when calculating the core area all individual areas marked that fully inside this contour area lie. Each individual area i, j contains in addition to the Information about the current shift including the corresponding one Information about previous shifts. Here, only those individual areas marked as belonging to the core, the in a predetermined number of previous shifts also represented or would represent core areas. The predetermined number depends on the desired number Shell thickness and the spatial distance between the individual areas; with layer thicknesses of 0.1mm and a shell thickness of 0.5mm For example, this number is 5. The same consideration also applies to subsequent layers: it only those individual areas are included in the core that in a given number of subsequent layers also belong to the core or would belong to it.

After assigning all individual areas to a shift the solidification by irradiating the layer within the Individual areas at the locations corresponding to the object. This radiation is now carried out in different ways and Way, depending on whether it is a single area in the core area or one in the envelope area. Since it is in Core area 2 (compared to the narrow envelope area 3) low warpage, low material consumption and If the construction times are short, the individual areas are there not irradiated over the entire area but in the form of individual cells or solidified, either by narrow Bridges or preferably not connected at all, but are separated by parting lines. Alternatively, it is possible the individual areas in the core area 2 only along closed Solidify lines, so that hollow structures such as Honeycomb structures result in which are still liquid or powdery material is included, which after the Solidification of the object either drained or by post-hardening is solidified. This method is particularly suitable to avoid thermal expansion, for example for melting molds, and also for direct production of molds. Here, the inverted object is converted into a enveloping cuboid. This creates a negative form on the one in the manner described above Disassembly into shell and core is made.

In core area 2, the radiation is carried out in such a way that that there is a high degree of polymerization and thus a high Strength with low tendency to warp results.

In the envelope area 3, on the other hand, there is high accuracy and quality of the surface on the contour 1. This is done the radiation or solidification in the envelope area 3 all over either in the form of side by side Hatching lines or one or more side by side Contour lines, i.e. the contour 1 for example as Polyline following line groups. Also a combination of these line types in a layer or in one on top of the other Layering is possible.

The radiation in the core area 2 and in the envelope area 3 one single layer can be simultaneously or in succession by appropriate control using a single or also several light beams or laser beams take place, whereby the layer thickness in core area 2 and envelope area 3 is equal to. However, it is particularly advantageous initially a number N of layers of the envelope region 3 solidify, where N is an integer. The material in the core area 2 initially remains liquid or powdery with a layer thickness that is N times the layer thickness of the Envelope area 3 corresponds. With the Nth layer too this thick layer of the core area by correspondingly intense Irradiation solidified. This can save time for the production of the core and thus for the production of the object can be significantly reduced.

If the core is not fully solidified, it is advantageous to provide openings in the shell through which the Core remaining liquid or powdery material after the solidification of the object can flow off. For example so that in every nth layer Breakthroughs of the envelope area 3 are provided, so are large enough to allow material to flow out, but do not affect the surface quality.

The particular advantage of the described method lies in that through the superimposed envelope areas 3 a relatively stable shell is made that it allowed the core area by means of a default minimizing technique without losing stability of the object suffers. For example, it's only because of this Cover possible on the connecting webs between the individual Dispense with cells or hollow structures in the core area. Furthermore, the manufacturing time is significantly reduced that at the core, which covers the vast majority of the Object volume forms, is only partially solidified.

Claims (17)

1. Process for producing a three-dimensional object, in which the object is created by successive solidifying of individual layers of liquid or powdered, solidifiable material by the action of an electromagnetic radiation, each layer being broken down into an inner core region (2) and an outer shell region (3) and that the action of radiation in the core region (2) and in the shell region (3) is controlled differently to create different properties of the two regions, characterized in that the shell region (3) is determined by subtraction in a three-dimensional way of individual regions of the core region (2) from the overall body.
2. Process according to Claim 1, characterized in that the action of radiation in the core region (2) takes place in such a way that the deformation of the object during and after the solidification is minimal, and in that the action of radiation in the shell region (3) takes place to create as smooth and accurate a surface as possible.
3. Process according to Claim 2, characterized in that, in the core region (2), individual spaced-apart subregions are solidified, and in that, if appropriate, the intermediate regions between the subregions are likewise solidified after solidifying the subregions of one layer or after solidifying all the subregions of the object.
4. Process according to Claim 2 or 3, characterized in that, in the core region (2), individual strips are solidified which are joined to neighbouring strips and strips lying underneath by means of a supporting structure are solidified.
5. Process according to Claim 2, characterized in that, in the core region (2), first of all subregions of one layer are solidified and are thereby joined to subregions lying underneath of the previously solidified layer to form multi-layered cells, in that thereafter the subregions are joined to the neighbouring subregions of the same layer by solidifying of narrow joining regions between the subregions in the form of joining webs, and in that finally the intermediate regions between the subregions are solidified.
6. Process according to Claim 5, characterized in that the joining regions are solidified only after a waiting time, which corresponds to a shrinkage of the subregions by at least a given amount.
7. Process according to Claim 3, characterized in that the subregions are formed to create hollow structures, preferably honeycomb structures.
8. Process according to one of the preceding claims, characterized in that, in the shell region (3), sub-regions lying closely next to one another are solidified.
9. Process according to one of the preceding claims, characterized in that the action of radiation in the shell region (3) takes place along one or more lines, which describe the outer edge of the shell region or are parallel to the latter.
10. Process according to one of the preceding claims, characterized in that the layer thickness in the shell region (3) is chosen to be less than in the core region.
11. Process according to Claim 10, characterized in that first of all a whole number N of layers of the shell region (3) are solidified and thereafter a layer of the core region (2) is solidified with a layer thickness corresponding to N times the thickness of the shell region layers.
12. Process according to one of the preceding claims, characterized in that, for the shell region (3), there are defined in a layer volume elements of the object which lie within a given distance from the edge of the object in this layer.
13. Process according to Claim 12, characterized in that those volume elements which are touched or intersected by the edge or the contour of the object in a layer and/or in a predetermined number of preceding and/or subsequent layers of this layer are defined.
14. Process according to one of the preceding claims, characterized in that, for the shell region (3), a thickness of 0.1 to 5 mm, preferably 0.5 to 2 mm, is chosen.
15. Process according to one of the preceding claims, characterized in that, in the shell region (3), openings through which the unsolidified material can flow out of the core region (2) are formed.
16. Process according to one of Claims 1 to 15, characterized in that the shell region (3) has a defined thickness, its width in a layer corresponding on average to approximately the side length of the individual regions.
17. Use of a process according to one of Claims 1 to 15 for producing casting moulds, the inverted object being placed into an enveloping block and a negative mould obtained from it, on which the breakdown into shell and core is performed.

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